Point-of-care (POC) sample analysis systems are generally based on one or more re-usable test instruments (e.g., a reading apparatus) that perform sample tests using a single-use disposable testing device, e.g., a cartridge or strip that contains analytical elements, e.g., electrodes or optics for sensing analytes such as pH, oxygen and glucose. The disposable testing device can include fluidic elements (e.g., conduits for receiving and delivering the sample to sensing electrodes or optics), calibrant elements (e.g., aqueous fluids for standardizing the electrodes with a known concentration of analyte), and dyes with known extinction coefficients for standardizing optics. The instrument or reading apparatus contains electrical circuitry and other components for operating the electrodes or optics, making measurements, and performing computations. The instrument or reading apparatus also has the ability to display results and communicate those results to laboratory and hospital information systems (LIS and HIS, respectively), for example, via a computer workstation or other data management system. Communication between the instrument or reading apparatus and a workstation, and between the workstation and a LIS or HIS, can be via, for example, an infrared link, a wired connection, wireless communication, or any other form of data communication that is capable of transmitting and receiving electrical information, or any combination thereof. A notable point-of-care system (The i-STAT® System, Abbott Point of Care Inc., Princeton, N.J.) is disclosed in U.S. Pat. No. 5,096,669, which comprises a disposable device, operating in conjunction with a hand-held analyzer, for performing a variety of measurements on blood or other fluids.
One benefit of point-of-care sample testing systems is the elimination of the time-consuming need to send a sample to a central laboratory for testing. Point-of-care sample testing systems allow a nurse or doctor (user or operator), at the bedside of a patient, to obtain a reliable quantitative analytical result, sometimes comparable in quality to that which would be obtained in a laboratory. In operation, the nurse selects a testing device with the required panel of tests, draws a biological sample from the patient, dispenses it into the testing device, optionally seals the testing device, and inserts the testing device into the instrument or reading apparatus. While the particular order in which the steps occur may vary between different point-of-care systems and providers, the intent of providing rapid sample test results close to the location of the patient remains. The instrument or reading apparatus then performs a test cycle, i.e., all the other analytical steps required to perform the tests. Such simplicity gives the doctor quicker insight into a patient's physiological status and, by reducing the turnaround time for diagnosis or monitoring, enables a quicker decision by the doctor on the appropriate treatment, thus enhancing the likelihood of a successful patient outcome.
Cardiac marker testing such as troponin testing is one such diagnostic test that benefits from the quicker turnaround time provided via POC sample analysis systems. National and international cardiology guidelines have recommended a one-hour turnaround time for reporting results of cardiac markers such as troponin to emergency department personnel, measured from the time of blood collection to reporting. The use of POC sample analysis systems reduce the turnaround times for reporting results of cardiac markers from that of central laboratory assays, but current POC sample analysis systems are not as precise or sensitive as central laboratory assays. In fact, the gap in precision and sensitivity between central laboratory assays and POC sample analysis systems is growing as manufacturers of central laboratory assays have or will release troponin assays that have a 99th percentile cutoff of about 10 ng/L and a limit of detection of <1 ng/L, which is presently not possible for current POC testing assays. These high-sensitivity assays are able to detect troponin in the majority of healthy subjects, and clinically, this allows for the detection of more cases of myocardial injury.
In order to compete analytically with these central laboratory assays, next generation POC testing assays will need to make technologic advancements. Thus there remains a need for systems and methods to extend the range of sensitivity for sample testing devices, e.g., single-use blood testing cartridges, used with one or more test instruments at the POC in a hospital or other location for delivering medical care.